Method of making quality crepe paper

ABSTRACT

The object of the present invention is to improve the adhesiveness of the paper body to the surface of a cylindrical Yankee dryer in the manufacturing process of crepe paper products in order to make a high-grade crepe form. 
     This is a manufacturing process of high-grade crepe paper products by attaching a paper body (P) to the surface of a rotating Yankee dryer (Y) and separating said paper body P through a doctor blade (D), wherein a crepe assistant (C) including 0.1 μg˜10 μg/m 2  of molybdenum disulfide is continuously fed directly onto the surface of the cylindrical Yankee dryer (Y) while the paper body P is continuously fed to the cylindrical Yankee dryer. 
     An improvement in the adhesiveness of the paper body brought about a lower crepe ratio and enabled to manufacture high-grade crepe paper products provided with uniformly fine and delicate crepe “microholds.”

TECHNICAL FIELD

This invention relates to a manufacturing process of crepe paperproducts and to a method of improving creping in the manufacturingprocess of crepe paper products in which a cylindrical Yankee dryer isused.

BACKGROUND ART

As the living standard improves in recent years, the demand for paperbody provided with crepe such as facial tissue, bath tissue, etc. hasrisen.

This paper body P provided with crepe or crepe paper is manufactured byattaching a paper body (wet paper) to the surface of a heated Yankeedryer Y, drying the same for a certain period of time, and separatingthe paper body P from the cylindrical Yankee dryer Y through a doctorblade D (see FIG. 2).

Incidentally, R represents a winding roll, R1 a touch roll and R2 anauxiliary roll.

To be more specific, the paper body P accumulates potential crepeforming power in the process of drying up while it is attached to thesmoothed surface of the dryer, and when it is separated from the surfaceof the cylindrical Yankee dryer by the doctor blade D, it formsinstantly curved crepes.

Now, the formation of a paper body P with a good creping requires theadhesiveness (close contact) of the paper body to a heated cylindricalYankee dryer Y, and its extent affects seriously the form of crepe.

In other words, it is known that, if the adhesiveness of the paper bodyto the cylindrical Yankee dryer is strong, the paper body P having beenseparated from the surface by the doctor blade forms fine and minutecrepes (or “microhold”) as shown in FIG. 3, and weak adhesiveness leadsto the formation of course crepes (or “macroholds”).

In addition, the more microholds are, the longer will be the length ofthe paper body produced (when no tension is applied) (the lower will bethe crepe ratio), and the more productivity improves.

On the other hand , the more macroholds are , the shorter will be thelength of the paper body produced (when no tension is applied) (thehigher will be the crepe ratio), and the lower productivity falls.

It should be noted here that adhesiveness is said to be correlative withthe smoothness of the dryer surface.

On the other hand, even under the impact of separation from the surfaceof the cylindrical Yankee dryer by the action of the doctor blade, anover-adhesion phenomenon of the paper body not separating from thesurface and passing under the doctor blade occurs.

As a result, the surface of the paper body is damaged or the surface ofthe cylindrical Yankee dryer is stained.

This is a phenomenon that occurs due to a poor releasability of thepaper body from the surface of the cylindrical Yankee dryer.

And this phenomenon become noticeable as the doctor blade getsincreasingly worn out, and paper body that has been produced tend oftento have macroholds constituting a qualitative disadvantage.

Therefore, in the normal operation, the doctor blades are replaced fourto eight times a day (every three to six hours) constituting an issuefor improving productivity.

Thus, it is necessary to guarantee contradicting matters, specificallythe adhesiveness of the paper body to the surface of the cylindricalYankee dryer and the releasability of the paper body from the surface ofthe cylindrical Yankee dryer.

In the meanwhile, an effective means used lately to improve productivityof paper with crepe is mainly to increase the surface speed of thecylindrical Yankee dryer, in other words to increase as much as possiblethe diameter of the cylindrical Yankee dryer.

However, the cylindrical Yankee dryers are made of casting from theviewpoint of thermal conductivity and temperature changes on thesurface, and the larger the diameter of the cylindrical Yankee dryer is(at present some of them has a diameter of six meters or more), theirsurface tend to become softer.

When they become soft, the action of the doctor blades in contact withthem causes naturally their surface to be worn and lose smoothness, andthe paper body becomes less adhesive to the cylindrical Yankee dryer.

For these reasons, at present an adhesive, or a adhesive and a releaseagent are applied on the cylindrical Yankee dryer to fill the unevennessof the dryer surface and to form a coating layer consisting of aadhesive and a release agent. (See e.g. Japanese Patent Application LaidOpen 2000-127597)

Although this method is certainly effective, but the coating layerformed by an adhesive is scraped by the doctor blade, the surface of thecoating layer itself becomes course and the resulting deterioration ofadhesivenss is a disadvantage.

Also the disadvantage of pulverized paper and adhesive cannot be treatedlightly.

The present invention is made with an intent of solving these variousissues.

In other words, the present invention has an object of improving theadhesiveness of the paper body to the surface of cylindrical Yankeedryer in the manufacturing process of paper body in which a cylindricalYankee dryer is used and to make a high- quality crepe form.

DISCLOSURE OF THE INVENTION

Thus the inventors of the present invention kept up their efforts toovercome these issues.

As a result, they found that the continuous application of a releaseagent, an adhesive and a crepe assistant including solid lubricants onthe surface of the cylindrical Yankee dryer resulted to their surprisein the development of a lubricant action between the doctor blade andthe cylindrical Yankee dryer, and as a result the wear and tear of afilm (coating layer) formed on the cylindrical Yankee dryer can bereduced to the minimum and the adhesion of the paper body can beimproved. Based on this finding, they completed the present invention.

Specifically, the present invention relates to (1) a manufacturingprocess of crepe paper products by attaching a paper body on the surfaceof a rotating cylindrical dryer, separating said paper body from saidsurface through the doctor blade, wherein a crepe assistant including afixed amount of solid lubricant is fed directly to the surface of thecylindrical Yankee dryer while the paper body is fed to the cylindricalYankee dryer.

And (2) the present invention relates to the manufacturing method ofhigh-quality crepe paper products according to item (1) wherein thesolid lubricant is a lamellar crystal type solid lubricant.

And (3) the present invention relates to the manufacturing method ofhigh-quality crepe paper products wherein the lamellar crystal typesolid lubricant is molybdenum disulfide.

And (4) the present invention relates to the manufacturing process ofhigh-quality crepe paper products according to item (3) wherein thepowder size of molybdenum disulfide is within a range of 0.1 μm˜10 μm.

And (5) the present invention relates to the manufacturing method ofhigh-quality crepe paper products according to item (3) wherein theamount of solid lubricant fed is within a range of 0.1 μg-μg/m².

And (6) the present invention relates to a manufacturing method ofhigh-quality crepe paper products wherein a paper body is attached tothe surface of a rotating cylindrical Yankee dryer and then said paperbody is separated from said surface through the doctor blade and a crepeassistant including molybdenum disulfide within a range of 0.1 μg-100μg/m² directly on the surface of the cylindrical Yankee dryer when thepaper body is fed to the cylindrical Yankee dryer.

And (7) the present invention relates to a manufacturing method ofhigh-grade crepe paper products wherein a paper body is attached to thesurface of a rotating cylindrical Yankee dryer and then said paper bodyis separated from said surface through the doctor blade and includingthe following steps 1) to 4):

1) The step of feeding a crepe assistant including a solid lubricantdirectly onto the surface of a rotating cylindrical Yankee dryer whilethe cylindrical Yankee dryer is operated to supply paper, the step of“supply chemicals”;

2) The step of forming film by feeding a crepe assistant including asolid lubricant and filling fine unevenness on the surface of thecylindrical Yankee dryer, the step of “forming a film”;

3) The step of producing a lubricating action between the doctor bladeand the cylindrical Yankee dryer, the “lubrication step”; and

4) The step of filling the worn-out portion of the film by the crepeassistant including a solid lubricant fed, the step of “replenishing thefilm”.

(Function)

The continuous provision of a fixed amount of crepe assistant includinga solid lubricant onto the surface of the cylindrical Yankee dryerresults in an efficient filling of fine unevenness on the surface of thedryer and the formation of a film (coating layer) smoothing its surface.

And at the same time, the solid lubricant contained in the crepeassistant fills fine unevenness of the surface.

On the other hand, the doctor blade is pressed against the film made ofa crepe assistant in order to separate a paper body from the surface ofthe cylindrical Yankee dryer. The solid lubricant contained in the film,however, produces a lubricating effect between the doctor blade and thesurface of the cylindrical Yankee dryer.

The further continued feeding of a crepe assistant replenishes a solidlubricant contained in the new crepe assistant to the worn-out film.

The present invention is described below by mentioning the mode of itscarrying out and by referring to drawings.

In general, the paper body with crepe is made by attaching said paperbody on the surface of the cylindrical Yankee dryer and by separatingthe same through the doctor blade.

As mentioned earlier, the paper body accumulates potential crepe formingpower as it is heated while remaining attached to the smoothed surfaceof the dryer, and when it is separated by the doctor blade from thesurface of the cylindrical Yankee dryer, it forms crepe instantly.

The method of improving creping according to the present invention is inprinciple applied to the cylindrical Yankee dryer. It improves theadhesiveness of the paper body to the dryer surface and improves thequality of the crepe form.

A method of improving the crepe form is to continue feeding a fixedamount of a crepe assistant including solid lubricant onto the surfaceof the cylindrical Yankee dryer.

In providing and feeding the crepe assistant, it is preferable to dilutethe same with water, and spray the same over the entire width of theYankee dryer.

This keeps a film (coating layer) of a crepe assistant including a solidlubricant formed on the dryer surface.

Here, for the solid lubricant, a lamellar crystal type is preferred inview of its low friction coefficient due to its cleavability.

As this lamellar crystal type, there are molybdenum disulfide, tungsten|disulfide, graphite fluoride, boron nitride, silicon nitride, etc., anyone or two of which are used alone or in combination.

Among these, molybdenum disulfide with its fine particulate of 0.1 μm˜10μm has a potential power of cleaving into 1,600 pieces or more, andbecause of its low friction coefficient (approximately 0.04) andmoreover its thermal and chemical stability, it is particularlypreferable as a solid lubricant.

As the crepe assistant, a crepe assistant that has been traditionallyused to improve creping is adopted.

A crepe assistant includes an adhesive and a release agent (mold releaseagent).

For the adhesive, epoxy resin which is a thermosetting resin, urearesin, and phenol resin are mentioned. Among these, it is particularlypreferable to use epoxy resin by dispersing it in a solvent (water).

For the release agent (mold release agent), there are oils (mineraloils, synthetic oils, vegetable oils, animal oils, etc.).

It is preferable to use Polybdenum or paraffin wax.

For actually feeding a crepe assistant including said solid lubricantonto the dryer surface, a spray nozzle S is used.

The spray nozzle S is disposed as shown in FIG. 2 between the doctorblades D (position shown by a solid line), or behind the doctor blade D(nozzle shown by a chain line with two dots).

As for the amount of a crepe assistant including a solid lubricant orlubricants, as expressed in terms of solid lubricant, the amount ofsolid lubricant to be sprayed will be within a range of 0.1 μg˜100μg/m².

When the amount of crepe assistant to be sprayed is less than 0.1 μg/m²,the crepe assistant does not attach in a sufficient quantity to thedryer surface, produces a relatively large amount of pulverized paperand the cycle of replacing the doctor blade becomes longer.

When the amount of crepe assistant to be sprayed exceeds 100 μg/m², theexcess amount will be absorbed in wet paper, and the effect will besaturated in terms of crepe ratio and the cycle of doctor replacement.

Now, a series of steps for feeding a crepe assistant including a solidlubricant or lubricants directly to the dryer surface will be describedbelow.

FIG. 1 is a schematic representation showing the principle of how thesurface of a cylindrical dryer will be treated.

1) Step of Feeding Chemicals

When a crepe assistant (chemical) C including a solid lubricant I is fedto the cylindrical Yankee dryer Y, the endless belt (felt) presses witha fixed pressure a paper sheet to the dryer, and the crepe assistant Cincluding the solid lubricant I fed to the dryer attaches to the dryersurface. (See A.)

The crepe assistant C including the solid lubricant I contains the solidlubricant 1, an adhesive and a release agent.

2) Step of Forming a Film

As a result of the continuous supply of the crepe assistant C includingthe solid lubricant 1, the crepe assistant C including the solidlubricant I attached to the dryer surface fills finely uneven parts(course areas) and forms a film (coating layer) several micron metersthick under heat and pressure applied (see B).

In this case, the solid lubricant I consisting of fine particles, as itis mixed in the crepe assistant, can easily penetrate evenly and in alarge quantify into the fine uneven part of the dryer surface. Thus thesolid lubricant is evenly distributed in the film.

Here, in the film (coating layer), a layer of release agent covering thefilm with adhesive (release mold agent layer 30) is formed (see B).

3) Lubrication Step

On the other hand, the film consisting of the crepe assistant Cincluding the solid lubricant I formed on the surface of the cylindricalYankee dryer Y is scraped by the doctor blade D at the same time as thepaper body P is separated from said surface. On the other hand, the filmbrings about lubricant effect between the doctor blade D and thecylindrical Yankee dryer Y. and consequently reduces frictions with thecylindrical Yankee dryer.

As a result, the wear and tear of the film of crepe assistant Cincluding solid lubricant I formed on the cylindrical Yankee dryer Y isreduced (see C).

In the meanwhile, when a paper body P is released from said surface, thelayer of release agent (release mold agent layer 30) covering the upperside of the film contributes to release smoothly the paper body P.

4) Step of Replenishing the Film

As the supply of the crepe assistant C including the solid lubricant Istill continues to the cylindrical Yankee dryer Y however, any decreaseresulting from the scraping by said doctor blade D will be immediatelyreplenished.

Incidentally, these actions 1) to 4) are not separated, but they areperformed at the same time in harmony.

As described above, by continuing to supply the crepe assistantincluding the solid lubricants on the new dryer surface in motion whilethe cylindrical Yankee dryer is operating, at the initial stage, thesteps 1) and 2) described above are executed.

Then, by continuing to supply the crepe assistant including the solidlubricant, the steps 3) to 4) described above are executed.

By passing through these four steps, i.e. the step of feeding chemicals,the step of forming a film, the lubrication step and the step ofreplenishing film, the function of feeding chemicals, the function offilling uneven parts, the function of lubricating between the dryer andthe doctor blade and the function of replenishing the worn out film areperformed.

As a result, on the dryer surface a film of crepe assistant including afixed amount of solid lubricant will be always maintained stably.

As the solid lubricant is uniformly dispersed in this film, while thedoctor blade remains pressed against the surface of the cylindricaldryer in order to separate the paper body from the cylindrical Yankeedryer, a so-called lubricating effect takes place between thecylindrical Yankee dryer and the doctor blade reducing frictions andpreventing possible wear of the doctor blade.

As the film contains uniformly distributed solid lubricants, it will bevery strong and robust.

Consequently, the amount of scraping by the doctor blade on the surfaceof the cylindrical Yankee dryer will be reduced and the wear and tear ofthe film will decrease.

In addition, when the paper body is separated by the doctor blade fromthe cylindrical Yankee dryer, an advantage of the system of the presentinvention is that the solid lubricant contributes to the release action.

As a result, the function of the release agent contained in the crepeassistant can be performed. According to the present invention, it ispossible to adopt a crepe assistant that does not necessarily contain arelease agent.

On the other hand, the surface of the film showing a low level offriction is always flat and smooth assuring an adhesiveness for thepaper body and the formation of fine and uniform crepes.

And when the paper body is released from the surface of the cylindricalYankee dryer, the release agent covering the upper side of the filmfunctions assuring releasability.

(Effect)

To sum up, the present invention has at least the following advantages.

As the adhesiveness of the paper body to the cylindrical Yankee dryerimproves, crepe ratio falls down and high-grade crepe paper productsprovided uniformly with fine and delicate crepe or “microholds” can beproduced.

In the course of manufacturing, the amount of pulverized paper generatedis limited, and the time consumed for cleaning machines is reduced.

The cycle of replacing doctor blades becomes longer and productivityimproves.

The electric power required to drive the dryer is reduced contributingto the economy of energy and cost reduction.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic functional illustration showing some principles ofhow the dryer surface is treated.

FIG. 2 is a schematic view showing the manufacturing method of crepepaper products by using a Yankee dryer.

FIG. 3 is a schematic view showing the microholds and macroholds in acrepe paper product.

THE BEST MODE FOR CARRYING OUT THE INVENTION

As for the amount of crepe assistant including solid lubricant to besprayed, it is necessary to spray little by little over the dryersurface, but the amount sprayed as expressed in terms of solid lubricantvaries within a range of 0.1 μg˜100 μg/m².

The test results of their spraying will be shown in the Examples below.

It should be noted however that the present invention is not necessarilylimited to the Examples shown below:

EXAMPLE 1

After 48 hours of spraying continuously a crepe assistant [consisting ofan adhesive (epoxy resin liquid) and a release agent (mineral oil)]including a solid lubricant (molybdenum disulfide) from the nozzle of asprayer onto the surface of a cylindrical Yankee dryer (made by KawanoyeIndustrial Co., Ltd.) used to manufacture crepe paper product (facialtissue), the dryer surface, the generation of pulverized paper, creperatio, the interval of replacing the doctor blades (replacement cycle)and the power for driving the dryer were observed.

Crepe paper (facial tissue): basis weight: 13 g

Paper width: 2,000 mm (2 m)

Paper processing speed: 730m/min.

Crepe Assistant Used Including Solid Lubricant

The crepe assistant used here is a mixture of an aqueous solution ofepoxy resin (AD400 (made by M)) and a solution obtained by diluting1,000 times a mineral oil liquid (DSL200 (made by M)) by water.

The ratio (by weight) of the aqueous solution of epoxy resin and themineral oil liquid before dilution is 1:2.5.

And the solid lubricant used is molybdenum disulfide, while the ratio(by weight) of the aqueous solution of epoxy resin and the solidlubricant added to the aqueous solution of epoxy resin is 40:1.

Amount Sprayed

And a fixed amount of a crepe assistant including a solid lubricant asmentioned above was fed (0.01 g/min. taking molybdenum disulfide as thestandard).

Specifically, the amount of solid lubricant sprayed (amount fed) overthe area of paper body fed to the Yankee dryer was 6.85 μg/m².

*(0.01 g/min)/(2×730 m/min)=6.85 μg/m²

Results Obtained After operating under the conditions mentioned abovewere as follows.

Results

The dryer surface looks like a mirror, and as shown in FIG. 1,exceedingly good results were obtained as compared with the priorexample 1 in terms of the appearance of pulverized paper, crepe ratio,replacement interval of doctor blades and the power required for drivingthe dryer.

EXAMPLE 2

Tests were conducted by reducing the amount sprayed from that of Example1 (the amount sprayed was 0.0002 g/min. taking molybdenum disulfide asthe standard).

Specifically, the amount of solid lubricant sprayed (amount fed) was0.14 μg/m².

Results.

The dryer surface looks like a mirror, and as shown in FIG. 1,exceedingly good results were obtained as compared with the priorexample 1 in terms of the appearance of pulverized paper, crepe ratio,replacement interval of doctor blades and the power required for drivingthe dryer.

However, the results were somewhat inferior to those of Example 1.

EXAMPLE 3

Tests were conducted by increasing the amount sprayed in Example 1 (theamount sprayed was 0.1 g/m in. taking molybdenum sulfide as thestandard)

Specifically, the amount of solid lubricant sprayed (amount fed) was68.5 μg/m².

Results

The dryer surface looks like a mirror, and as shown in FIG. 1,exceedingly good results were obtained as compared with the priorExample 1 in terms of the appearance of pulverized paper, crepe ratio,the replacement interval of doctor blades and the power required fordriving the dryer.

Compared with Example 1, however, there were no great differences otherthan those related to power consumption.

EXAMPLE 4

Tests were conducted by increasing the amount sprayed in Example 1 (theamount sprayed was 0.15 g/min. taking molybdenum sulfide as thestandard)

Specifically, the amount of solid lubricant sprayed (amount fed) was102.75 μg/m².

Results

In general, as shown in Table 1, the results obtained were not muchdifferent from those of Example 3.

Example for comparison 1

Similar tests were conducted in Example 1 by using an organic solidlubricant other than lamellar crystal type [MCA (melamine cyanurate)] inplace of molybdenum disulfide (the amount sprayed was 0.05 g/min. takingMCA as the standard).

Specifically, the amount of solid lubricant sprayed (amount fed) was34.25 μg/m².

Results

The dryer surface is relatively course, and as shown in FIG. 1, theresults obtained were somewhat inferior to Examples 1 through 4 in termsof the appearance of pulverized paper, crepe ratio, the replacementinterval of doctor blades and the power required to drive the dryer.

Example for comparison 2

Similar tests were conducted in Example 1 by using the same crepeassistant but without adding any solid lubricant (the amount of crepeassistant sprayed was the same as in Example 1).

Specifically, the amount of solid lubricant sprayed (amount fed) wasnil.

Results

The dryer surface was very course and rugged, and as shown in FIG. 1,the results obtained were extremely bad as compared with Examples 1through 4 in terms of the appearance of pulverized paper, crepe ratio,the replacement interval of doctor blades and the power required todrive the dryer.

TABLE 1 Pulverized paper Replacement Crepe (compared with Power to drivecycle of ratio Example for the dryer doctor blades (%) comparison 2)(KW/h) Example 1 32 12.5  1/10 174 Example 2 12 13.5 1/5 178 Example 336 12.0  1/10 172 Example 4 38 12.0  1/10 172 Example for 6 15.0 1/3 185comparison 1 Example for 4 15.0 1* 185 comparison 2 *5 Kg/24 hours

So far, the present invention has been described, but the presentinvention is not limited to the examples of carrying out given above,and it is needless to say that other various variations are possible tothe extent that they do not deviate from the essence.

For example, a cylindrical Yankee dryer was shown for explanation on thedryer. However, the present invention can be applied to any means ofmanufacturing a paper body with crepe by releasing the same from a dryerthrough a doctor blade.

And in the examples given above, the case of facial tissue was cited asan example of paper body to which the present invention can be applied.The inventors have confirmed similar effects on bath tissues, however.

INDUSTRIAL APPLICABILITY

As described above, the manufacturing process of high-grade crepe paperproducts related to the present invention is a technology applicable tothe manufacturing method of crepe paper products by means of thecylindrical Yankee dryer. However, it is applicable to the entiretechnological field of the paper making industry to the extent thatsimilar effects can be expected therefrom.

What is claimed is:
 1. A method of manufacturing high-grade crepe paperproducts by attaching a paper body to the surface of a rotatingcylindrical dryer and separating said paper body from said surfacethrough a doctor blade, wherein a crepe assistant including a fixedamount of molybdenum disulfide and an adhesive is continuously feddirectly to the surface of the cylindrical Yankee dryer while the paperbody is fed to the cylindrical Yankee dryer.
 2. The manufacturing methodof high-grade crepe paper products according to claim 1 wherein theparticle size of molybdenum disulfide is within a range of 0.1 μm to 10μm.
 3. The manufacturing method of high-grade crepe paper productsaccording to claim 1 wherein the amount of molybdenum disulfide fed iswithin a range of 0.1 μg to 100 μg/m².
 4. A method of manufacturinghigh-grade crepe paper products by attaching a paper body to the surfaceof a rotating cylindrical dryer and separating said paper body from saidsurface through a doctor blade, wherein a crepe assistant including 0.1μg to 100 μg/m² of molybdenum disulfide is continuously fed directly tothe surface of the cylindrical Yankee dryer while the paper body is fedto the cylindrical Yankee dryer.
 5. A method of manufacturing high-gradecrepe paper products by attaching a paper body to the surface of arotating cylindrical dryer and then separating said paper body from saidsurface through a doctor blade, said method comprising: 1) the feedingstep of feeding a crepe assistant including a molybdenum disulfide andan adhesive directly to the surface of a rotating cylindrical Yankeedryer while paper is fed by the operation of the cylindrical Yankeedryer; 2) the step of forming a film by feeding a crepe assistantincluding the molybdenum disulfide and the adhesive and filling fineuneven parts of the surface of the cylindrical Yankee dryer; 3) the stepof filing creating a lubricating effect between the doctor blades andthe cylindrical Yankee dryer; and 4) the step of filling any worn outparts of the film with the crepe assistant including the molybdenumdisulfide and the adhesive fed.